Various musical effects are achieved by the skilled organist, which the unskilled player cannot achieve. These include arpeggio effects, in which the organist rapidly ascends the keys of the organ, in any of a variety of fanciful sequences, or ascends and then descends. If the sequence covers a short range of notes the effect is called a strum, simulating the sound of a strummed guitar, so that a strum may be considered a short ascending arpeggio. Heretofore, it has not been possible to achieve strums or arpeggios automatically, in response to playing of one or more notes of a manual of an organ. The present invention provides automatic arpeggiation for the accompaniment manual of an electronic organ, and is believed to be a pioneer invention in this respect.
One problem faced in designing an arpeggiator is that there are sixty-one keys in the usual accompaniment manual, so that if all notes were to be controlled an extremely complex arpeggiator would result. According to the present invention, notes are grouped by threes, on the assumption that two or three notes of each trio will seldom be called forth simultaneously, so that each trio can be treated as one note for purposes of arpeggiation. The arpeggiator is thus required to deal with only twenty note positions, one of these accommodating four notes instead of three.
Trios of tone gates are turned on individually by key switches, as is usual in an organ, but each group of three tone signal gates controls one further gate which is arranged for wave shaping to produce piano-like tones. The latter gates are called pulse gates, and the key switch controlled gates are called key gates. The key gates are short sustain gates, and the pulse gates are long sustain linear gates.